A fluid jet exiting from a garden hose or fire hose generates a reaction force of a magnitude equal to the fluid density times the square of the fluid velocity in a direction opposite to the direction of the fluid jet. As the magnitude of the reaction of the fluid flow is proportional to the square of the fluid velocity, the reaction of the fluid flow can be used as a measure of the mass or volume flow rate of fluid, which method is particularly useful in measuring low flow rate of fluid. For example, the minimum velocity of air flow under the standard condition measurable by the best industrial flowmeter available at the present time is in the range of 5 to 10 feet per second. The reaction force of the flow resulting from the air flow at these velocities is in the range of 1 to 4 ounces, which is large enough force readily measurable without using an exotic force measuring device. In general, determining the flow rates of gaseous media with low density from the measured value of the reaction force of the flow that is proportional to the square of the media velocity, provides a definite advantage in measuring low flow rates over other methods involving a direct measurement of the fluid velocity or mass flow rate. As the most cases of the industrial measurements of liquid flows deal with the media velocities greater than 1 foot per second, measuring the square of the velocity in place of the velocity itself does not create any disadvantage in general. In conclusion, a flowmeter determining the flow rates from the reaction force of the flow provides an useful alternative to the existing versions of the flowmeters directly measuring the mass or volume flow rates. While the reaction force created by a fluid jet exiting from the free end of a hose or tubing can be readily felt by a person holding the hose or tubing and easily measured by a simple set up employing a spring balance or other force measuring device, the measurement of the reaction force of the flow of a fluid moving through a continuous conduit as a measure of fluid flow with an accuracy required by the standard of industrial flow measurements demands a novel arrangement and ingenious principles.